The overall research objective is to develop a neurovascular model of the dental pulp tissue by determining the relationship between pulpal blood flow and pulpal sensory nerve activity. The specific objective of this proposal is to test the sensitivity of A-delta and C-fiber activities to hypoxia by a decrease in oxygen supply to the pulp. Pulpal hemodynamics in dogs will be altered by a gradual mechanical constriction of the inferior alveolar artery and by systemic hemodilution. Hemodilution will be achieved by an isovolumic systemic exchange of plasma and blood to decrease the hematocrit level to 15-20%. The Xenon-133 washout method will be used to measure pulpal blood flow. Intradental nerve activity will be monitored from the dentinal cavities, and from single fibers in the inferior alveolar nerve. Electrical and chemical stimulation of the pulpal nerves will provide the means of exciting sensory nerve fibers (eg. A-delta and C-fibers) in the pulp. Simultaneous monitoring of intradental nerve activity from the dentin cavities and single fibers of the inferior alveolar nerve following tooth stimulation during experimental manipulation of pulpal hemodynamics will provide the necessary information for a cross-correlation between blood flow and neural activity in the pulp. This project, using a multidisciplinary approach of combined circulatory and neurophysiological methods may provide additional insights to elucidate physiological mechanisms of pulpal sensitivity and ultimately shed light on the pathophysiological mechanisms of pulpitis and hypersensitive teeth.